Superconducting interposer for the transmission of quantum information for quantum error correction

ABSTRACT

A system for transmission of quantum information for quantum error correction includes an ancilla qubit chip including a plurality of ancilla qubits, and a data qubit chip spaced apart from the ancilla qubit chip, the data qubit chip including a plurality of data qubits. The system includes an interposer coupled to the ancilla qubit chip and the data qubit chip, the interposer including a dielectric material and a plurality of superconducting structures formed in the dielectric material. The superconducting structures enable transmission of quantum information between the plurality of data qubits on the data qubit chip and the plurality of ancilla qubits on the ancilla qubit chip via virtual photons for quantum error correction.

BACKGROUND

Currently claimed embodiments of the present invention relate to systemsand methods for quantum error correction, and more specifically, to asuperconducting interposer for the transmission of quantum informationfor quantum error correction.

As the number of qubits on a given quantum processor increases, itbecomes necessary to move quantum information between qubits fabricatedon separate chips, especially for applications such as quantum errorcorrection. The current state of the art uses planar structures, such asbus resonators, to transmit quantum information between qubits.

SUMMARY

According to an embodiment of the present invention, a system fortransmission of quantum information for quantum error correctionincludes an ancilla qubit chip including a plurality of ancilla qubits,and a data qubit chip spaced apart from the ancilla qubit chip, the dataqubit chip including a plurality of data qubits. The system includes aninterposer coupled to the ancilla qubit chip and the data qubit chip,the interposer including a dielectric material and a plurality ofsuperconducting structures formed in the dielectric material. Thesuperconducting structures enable transmission of quantum informationbetween the plurality of data qubits on the data qubit chip and theplurality of ancilla qubits on the ancilla qubit chip via virtualphotons for quantum error correction.

According to an embodiment of the present invention, a method oftransmitting quantum information for quantum error correction includesproviding a plurality of ancilla qubits, and providing a plurality ofdata qubits spaced apart from the plurality of ancilla qubits. Themethod includes mapping errors from the plurality of data qubits to theplurality of ancilla qubits via virtual photons in a superconductingmicrowave transmission line, and measuring the plurality of ancillaqubits to detect the errors. The method includes performing quantumerror correction based on the detected errors.

According to an embodiment of the present invention, a quantum computerincludes a refrigeration system under vacuum including a containmentvessel. The system includes an ancilla qubit chip contained within arefrigerated vacuum environment defined by the containment vessel, theancilla qubit chip including a plurality of ancilla qubits. The systemincludes a data qubit chip contained within the refrigerated vacuumenvironment defined by the containment vessel. The data qubit chip isspaced apart from the ancilla qubit chip and includes a plurality ofdata qubits. The system includes an interposer contained within therefrigerated vacuum environment defined by the containment vessel. Theinterposer is coupled to the ancilla qubit chip and the data qubit chipand includes a dielectric material and a plurality of superconductingstructures formed in the dielectric material. Superconducting resonatorscomprising the superconducting structures formed in the interposerenable transmission of quantum information between the plurality of dataqubits on the data qubit chip and the plurality of ancilla qubits on theancilla qubit chip via virtual photons for quantum error correction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a system for transmission ofquantum information for quantum error correction according to anembodiment of the invention.

FIG. 2A is a schematic illustration of a top-down view of an ancillaqubit chip according to an embodiment of the current invention.

FIG. 2B is a schematic illustration of a top-down view of an interposeraccording to an embodiment of the current invention.

FIG. 2C is a schematic illustration of a top-down view of a data qubitchip according to an embodiment of the current invention.

FIG. 2D is a schematic illustration of a top-down view of the interposerof FIG. 2B coupled to the ancilla chip of FIG. 2A and the data chip ofFIG. 2C according to an embodiment of the current invention.

FIG. 3 is a schematic illustration of an ancilla qubit chip thatincludes an ancilla qubit and an ancilla measurement resonatorconfigured for measurement of the ancilla qubit according to anembodiment of the current invention.

FIG. 4 is a schematic illustration of a data qubit chip that includes adata qubit and a data measurement resonator configured for measurementof the data qubit according to an embodiment of the current invention.

FIG. 5 is a schematic illustration of the ancilla qubit chip of FIG. 3coupled to the data qubit chip of FIG. 4 by an interposer according toan embodiment of the current invention.

FIG. 6 is a schematic illustration of an ancilla qubit chip and a dataqubit chip coupled to the same surface of an interposer.

FIG. 7 is a schematic illustration of a system for transmission ofquantum information for quantum error correction according to anembodiment of the current invention.

FIG. 8 is a flowchart that illustrates a method of transmitting quantuminformation for quantum error correction according to an embodiment ofthe current invention.

FIG. 9 is a schematic illustration of a quantum computer according to anembodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 is a schematic illustration of a system 100 for transmission ofquantum information for quantum error correction according to anembodiment of the invention. The system 100 includes an ancilla qubitchip 102 comprising a plurality of ancilla qubits 104, 106, 108. Thesystem 100 includes a data qubit chip 110 spaced apart from the ancillaqubit chip 102. The data qubit chip 110 comprising a plurality of dataqubits 112, 114, 116. The system 100 includes an interposer 118 coupledto the ancilla qubit chip 102 and the data qubit chip 110. Theinterposer 118 includes a dielectric material 120 and a plurality ofsuperconducting structures 122, 124, 126 formed in the dielectricmaterial 120. The superconducting structures 122, 124, 126 enabletransmission of quantum information between the plurality of data qubits112, 114, 116 on the data qubit chip 110 and the plurality of ancillaqubits 104, 106, 108 on the ancilla qubit chip 102 via virtual photonsfor quantum error correction.

As shown in FIG. 1, the interposer 118 according to an embodiment of theinvention includes a first surface 128 and a second surface 130 oppositethe first surface 128. The ancilla qubit chip 102 is coupled to thefirst surface 128 of the interposer 118, and the data qubit chip 110 iscoupled to the second surface 130 of the interposer 118.

According to an embodiment of the current invention, eachsuperconducting structure of the plurality of superconducting structuresextends from a data qubit of the plurality of data qubits to an ancillaqubit of the plurality of ancilla qubits. For example, in FIG. 1, thesuperconducting structure 122 extends from the data qubit 112 to theancilla qubit 104. According to an embodiment of the current invention,the data qubit 112 has a first frequency, the ancilla qubit 104 has asecond frequency, and a superconducting resonator comprising thesuperconducting structure 122, the solder bumps 132 and 138, and theright-angle capacitor couplers on chips 102 and 110 has a thirdfrequency. The superconducting structure 122 formed in the interposerallows the transmission of quantum information because it forms a partof a superconducting resonator. The superconducting resonator may alsoinclude the solder bumps 132 and 138 and as well as structures on theancilla and data qubit chips that are galvanically coupled to the solderbumps 132 and 138. The structures on the ancilla and data qubit chipsmay be coplanar waveguide transmission lines, as is the case in thefigures, although embodiments of the invention are not limited tocoplanar waveguide transmission lines. In some embodiments, thesuperconducting structure 122 itself may form the superconductingresonator.

The frequency of the superconducting resonator, referred to herein asthe third frequency, is sufficiently detuned from the first frequencyand the second frequency to prevent real photon transfer between thedata qubit and the ancilla qubit. Instead, quantum information istransferred from the data qubit 112 and the ancilla qubit 104 by virtualphoton transfer. Virtual photon transfer ensures that the quantuminformation stored in the data qubit 112 is immune from theelectromagnetic Purcell effect. Virtual photon transfer also protectsthe quantum information from the effects of dielectric loss of theinsulating material forming the interposer 118.

According to an embodiment of the invention, the ancilla qubit chip isbonded to the interposer. In FIG. 1, the ancilla qubit chip 102 isbonded to the interposer 118 using a plurality of solder bumps 132, 134,136. The solder bumps couple the ancilla qubits 104, 106, 108 to thesuperconducting structures 122, 124, 126. As shown in FIG. 1, the solderbumps may be galvanically coupled to the superconducting structures 122,124, 126, and capacitively coupled the ancilla qubits 104, 106, 108.Embodiments of the current invention are not limited to the particularnumber of ancilla qubits, data qubits, and superconducting structures,and solder bumps shown in FIG. 1.

According to an embodiment of the invention, the data qubit chip isbonded to the interposer. In FIG. 1, the data qubit chip 110 is bondedto the interposer 118 using a plurality of solder bumps 138, 140, 142.As shown in FIG. 1, the solder bumps may be galvanically coupled to thesuperconducting structures 122, 124, 126, and capacitively coupled tothe data qubits 112, 114, 116. The solder bumps may be formed from asuperconducting material, although the embodiments of the invention arenot limited to solder bumps formed from superconducting materials. Oneexample material for the solder bumps is indium. The system 100according to an embodiment of the present invention may include multipleancilla qubit chips and data qubit chips. The ancilla qubit chips anddata qubit chips may be bonded to a single interposer, or to multipleinterposers.

FIG. 2A is a schematic illustration of a top-down view of an ancillaqubit chip 200 according to an embodiment of the current invention. Theancilla qubit 200 includes three ancilla qubits 202, 204, 206. However,ancilla qubit chips according to other embodiments of the currentinvention are not limited to any particular number of ancilla qubits.There can be more than three, or less than three ancilla qubits in otherembodiments.

FIG. 2B is a schematic illustration of a top-down view of an interposer208. The interposer includes a plurality of superconducting structures210, 212, 214, 216. The superconducting structures may besuperconducting vias, for example. The superconducting vias could bepart of superconducting transmission line resonators that are partiallyor wholly formed within the interposer. The superconducting structuresmay be formed from one or more of niobium, aluminum, tin, electroplatedrhenium, or indium, for example. Although the embodiment of FIG. 2Bshows an example of four superconducting structures 210, 212, 214, 216,other embodiments could have less than four or more than four.

FIG. 2C is a schematic illustration of a top-down view of a data qubitchip 218. The data qubit chip 218 includes two data qubits 220, 222.Other embodiments of data qubit chips could have more than or less thantwo data qubits.

FIG. 2D is a schematic illustration of a top-down view of the interposercoupled to the ancilla chip and the data chip. The ancilla qubits 202,204, 206 and the data qubits 220, 222 are connected to each other by thesuperconducting structures 210, 212, 214, 216.

Embodiments of the current invention enable transmission of quantuminformation for quantum error correction. Quantum error correction oftenrequires a large number of data qubits and ancilla qubits to be coupledto each other. The data qubit are qubits that have relatively longrelaxation and coherence times, while the ancilla qubits may be qubitsthat have relatively short relaxation and coherence times. Quantuminformation is spread over a collection of data qubits. The data qubitsare coupled to ancilla qubits such that errors in the quantuminformation are mapped form the data qubits to the ancilla qubits. Theancilla qubits can be measured to detect and/or correct the errors.

Quantum error correction algorithms, such as, but not limited to, theSurface Code, the Shor Code, and the Steane Code require frequentmeasurements of the ancilla qubits. These measurements provideinformation about the data qubits to which the ancilla qubits arecoupled, and also stabilize the data qubits. The frequency of themeasurements necessitates fast measurements, which require strongcoupling between the measurement resonators coupled to the ancillaqubits and the environment. Although the strong coupling enables fastmeasurement of the ancilla qubits, it also makes the ancilla qubits moresusceptible to environmental noise and increases the spontaneous decayrate of the ancilla qubits through the Purcell effect. This strongcoupling, if made to the data qubits, would shorten the lifetime of thequantum states in the data qubits.

Embodiments of the current invention enable strong coupling between theancilla qubits and the environment, while reducing the coupling betweenthe data qubits and the environment. The ancilla qubits are physicallyseparated from the data qubits, and are coupled to the data qubits bysuperconducting structures formed in the interposer.

The physical separation also allows different materials and processes tobe used for the formation of the data qubit chip and the ancilla qubitchip. Although both chips may include a plurality of qubits, the qualityrequirements for the data qubits and ancilla qubits may be verydifferent. The requirements for the ancilla qubits may be based on howfrequently they are measured. According to some embodiments, the ancillaqubit measurement cycle may be about 1 μs, so the ancilla qubits mayhave coherence times greater than 1 μs, for example, on the order of afew microseconds. The material requirements for such qubits are not asstringent as those used to fabricate higher quality qubits, such as thedata qubits. Further, the ancilla qubit chip can be formed and modifiedusing fabrication methods such as lithography that can change thefrequency of the ancilla qubits. The ancilla qubit chip can also beformed such that the ancilla qubits are tunable qubits. While havingtunable qubits can aid in system control, the process of forming thetunable qubits can require breaking the ground plane of the microwaveresonators coupled to the qubits. This could be undesirable for the dataqubits because of the introduction of flux noise susceptibility andspurious microwave modes, but may be acceptable for the ancilla qubits,which are allowed a shorter coherence time.

According to an embodiment of the current invention, the interposerincludes a dielectric material that is, for example, a printed circuitboard, an organic laminate, a silicon chip, a ceramic, aglass-reinforced epoxy laminate material such as FR-4, duroid, orpolyether ether ketone (PEEK).

According to an embodiment of the current invention, the ancilla qubitchip includes ancilla measurement resonators coupled to the plurality ofancilla qubits. The ancilla measurement resonators are configured formeasurement of the plurality of ancilla qubits. The ancilla measurementresonators may be, for example, superconducting microwave coplanarwaveguide resonators. FIG. 3 is a schematic illustration of an ancillaqubit chip 300 that includes an ancilla qubit 302 and an ancillameasurement resonator 304 configured for measurement of the ancillaqubit 302. The ancilla measurement resonator 304 may capacitively coupleto the ancilla qubit 302 to measurement and control instruments. FIG. 3shows a capacitor 306 that capacitively couples the ancilla measurementresonator 304 and the ancilla qubit 302 to a port 308 with measurementand control instruments.

According to an embodiment of the current invention, the data qubit chipincludes data measurement resonators coupled to the plurality of dataqubits. The data measurement resonators may be, for example,superconducting microwave resonators. FIG. 4 is a schematic illustrationof a data qubit chip 400 that includes a data qubit 402 and a datameasurement resonator 404 configured for measurement of the data qubit402. FIG. 4 shows a capacitor 406 that capacitively couples the datameasurement resonator 404 and the data qubit 402 to a port 408 formeasurement and control instruments.

FIG. 5 is a schematic illustration of the ancilla qubit chip 300 of FIG.3 coupled to the data qubit chip 400 of FIG. 4 by an interposer. Asshown in FIG. 5, the capacitor 500 coupling the ancilla qubit 502 andthe ancilla measurement resonator 504 to measurement and controlinstruments is much larger than the capacitor 506 coupling the dataqubit 508 and the data measurement resonator 510 to measurement andcontrol instruments. The strong coupling between the ancilla measurementresonator 504 and the readout electronics enables fast measurement ofthe ancilla qubit 502. This is useful for quantum error correction,which may require measurement cycles on the order of one per 1 μs. Incontrast, the data measurement resonator 510 is weakly coupled to themeasurement electronics because the data qubit 508 may only be read whenthe quantum algorithm is complete, instead of every 1 μs. A longermeasurement time may be used to make up for the weak coupling. The weakcoupling between the data qubit 508 and the measurement electronicshelps preserve the coherence of the data qubit 508. The data qubit 508may have relaxation and coherence times that are greater than 75 μs, forexample. The data qubit 508 may have relaxation and coherence times thatare on the order of 100 μs, for example.

As an alternative to the configuration shown in FIG. 1, the ancillaqubit chip and the data qubit chip may be coupled to the same surface ofthe interposer. FIG. 6 is a schematic illustration of an ancilla qubitchip 600 and a data cubit chip 602 coupled to the same surface 604 of aninterposer 606.

According to an embodiment of the current invention, for each data qubitof the plurality of data qubits, the superconducting structures enabletransmission of quantum information between the data qubit and at leasttwo ancilla qubits of the plurality of ancilla qubits. Similarly, foreach ancilla qubit of the plurality of ancilla qubits, thesuperconducting structures may enable transmission of quantuminformation between the ancilla qubit and at least two data qubits ofthe plurality of data qubits. Quantum information can be mapped from atleast two data qubits to ancilla qubits to allow measurement of aneigenstate of the data qubits, so that performing the measurement doesnot destroy the quantum information.

FIG. 7 is a schematic illustration of a system 700 for transmission ofquantum information for quantum error correction according to anembodiment of the current invention. An ancilla qubit 702 on the ancillaqubit chip 704 is coupled to two superconducting structures 706, 708.The superconducting structures enable transmission of quantuminformation between the ancilla qubit 702 and two data qubits 710, 712.Another superconducting structure 714 enables transmission of quantuminformation between the data qubit 712 and a second ancilla qubit 716.Although only two of the qubits in FIG. 7 are illustrated as beingcoupled to two other qubits, each of the qubits on the ancilla chip andthe data chip may be coupled to two or more qubits on the other chip bysuperconducting structures. Quantum error correction codes, such as theSurface Code, for example, may require that each data qubit be coupledto multiple ancilla qubits, and each ancilla qubit be coupled tomultiple data qubits. In the example of the Surface Code, errors can bemapped from the data qubits to the ancilla qubits using CNOT gates, viavirtual photons exchanged through the superconducting structures.Measurement of the ancilla qubits may give the parity of the dataqubits, for example in the Surface Code. Since parity is an eigenvalueof the Bell state, measurement of the ancilla qubits stabilizes thequantum information in the data qubits. Although the Surface Code isdiscussed herein, the embodiments of the current invention are notlimited to the Surface Code. Other quantum error correction algorithmsmay be used.

FIG. 8 is a flowchart that illustrates a method 800 of transmittingquantum information for quantum error correction according to anembodiment of the current invention. The method 800 includes providing aplurality of ancilla qubits 802, and providing a plurality of dataqubits 804 spaced apart from the plurality of ancilla qubits. The method800 includes mapping errors from the plurality of data qubits to theplurality of ancilla qubits via virtual photons in a superconductingmicrowave transmission line 806. The method 800 further includesmeasuring the plurality of ancilla qubits to detect the errors 808, andperforming quantum error correction 810 based on the detected errors.

According to an embodiment of the invention, measuring the plurality ofancilla qubits 808 gives a parity of the plurality of data qubits.

FIG. 9 is a schematic illustration of a quantum computer 900 accordingto an embodiment of the present invention. The quantum computer 900includes a refrigeration system under vacuum including a containmentvessel 902. The quantum computer 900 includes an ancilla qubit chip 904contained within a refrigerated vacuum environment defined by thecontainment vessel 902. The ancilla qubit chip 904 includes a pluralityof ancilla qubits 906, 908, 910. The quantum computer 900 includes adata qubit chip 912 contained within the refrigerated vacuum environmentdefined by the containment vessel 902. The data qubit chip 912 is spacedapart from the ancilla qubit chip 904 and includes a plurality of dataqubits 914, 916, 918. The quantum computer 900 includes an interposer920 contained within the refrigerated vacuum environment defined by thecontainment vessel 902. The interposer 920 is coupled to the ancillaqubit chip 904 and the data qubit chip 912 and includes a dielectricmaterial 922 and a plurality of superconducting structures 924, 926, 928formed in the dielectric material 922. The superconducting structures924, 926, 928 enable transmission of quantum information between theplurality of data qubits 914, 916, 918 on the data qubit chip 912 andthe plurality of ancilla qubits 906, 908, 910 on the ancilla qubit chip904 via virtual photons for quantum error correction.

The quantum computer according to an embodiment of the current inventionmay include a plurality of ancilla qubit chips, data qubit chips, andinterposers. Further, the embodiments of the invention are not limitedto the particular number of ancilla qubits, data qubits, andsuperconducting structures, and solder bumps shown in FIG. 9.

Embodiments of the current invention enable transfer of quantuminformation using a dielectric interposer with partially embeddedmicrowave transmission line bus resonators. The quantum information iscommunicated via virtual photons in the resonators. The use of virtualphotons ensures that quantum information is not lost due to theelectromagnetic Purcell effect or the dielectric loss of the material.By separating qubit chips into those that include data qubits(long-lived, high quality qubits) and those that include ancilla qubits(need fast measurement and control, and are therefore more susceptibleto loss channels), errors may be mapped onto the ancilla qubits usingthe superconducting interposer.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

We claim:
 1. A system for transmission of quantum information forquantum error correction, comprising: an ancilla qubit chip comprising aplurality of ancilla qubits; a data qubit chip spaced apart from saidancilla qubit chip, said data qubit chip comprising a plurality of dataqubits; and an interposer coupled to said ancilla qubit chip and saiddata qubit chip, said interposer comprising a dielectric material and aplurality of superconducting structures formed in said dielectricmaterial, wherein said superconducting structures enable transmission ofquantum information between said plurality of data qubits on said dataqubit chip and said plurality of ancilla qubits on said ancilla qubitchip via virtual photons for quantum error correction.
 2. The system fortransmission of quantum information for quantum error correctionaccording to claim 1, wherein said ancilla qubit chip further comprisesancilla measurement resonators coupled to said plurality of ancillaqubits, said ancilla measurement resonators configured for measurementof said plurality of ancilla qubits.
 3. The system for transmission ofquantum information for quantum error correction according to claim 2,wherein said data qubit chip further comprises data measurementresonators coupled to said plurality of data qubits, said datameasurement resonators configured for measurement of said plurality ofdata qubits.
 4. The system for transmission of quantum information forquantum error correction according to claim 3, wherein the ancillameasurement resonators are coupled to measurement electronics morestrongly than said data measurement resonators are coupled to saidmeasurement electronics.
 5. The system for transmission of quantuminformation for quantum error correction according to claim 1, whereinsaid interposer comprises a first surface and a second surface oppositesaid first surface, and wherein said ancilla qubit chip is coupled tosaid first surface of said interposer, and said data qubit chip iscoupled to said second surface of said interposer.
 6. The system fortransmission of quantum information for quantum error correctionaccording to claim 1, wherein said ancilla qubit chip and said datacubit chip are coupled to a same surface of said interposer.
 7. Thesystem for transmission of quantum information for quantum errorcorrection according to claim 1, wherein each superconducting structureof said plurality of superconducting structures extends from a dataqubit of said plurality of data qubits to an ancilla qubit of saidplurality of ancilla qubits.
 8. The system for transmission of quantuminformation for quantum error correction according to claim 1, whereinsaid data qubit has a first frequency, said ancilla qubit has a secondfrequency, and a superconducting resonator comprising thesuperconducting structure formed in the interposer has a thirdfrequency, wherein said third frequency is sufficiently detuned fromsaid first frequency and said second frequency to prevent real photontransfer between said data qubit and said ancilla qubit.
 9. The systemfor transmission of quantum information for quantum error correctionaccording to claim 1, wherein, for each data qubit of said plurality ofdata qubits, said superconducting structure enables transmission ofquantum information between said data qubit and at least two ancillaqubits of said plurality of ancilla qubits.
 10. The system fortransmission of quantum information for quantum error correctionaccording to claim 1, wherein, for each ancilla qubit of said pluralityof ancilla qubits, said superconducting structures enable transmissionof quantum information between said ancilla qubit and at least two dataqubits of said plurality of data qubits.
 11. The system for transmissionof quantum information for quantum error correction according to claim1, wherein said ancilla qubit chip is bonded to said interposer.
 12. Thesystem for transmission of quantum information for quantum errorcorrection according to claim 1, wherein said data qubit chip is bondedto said interposer.
 13. The system for transmission of quantuminformation for quantum error correction according to claim 1, whereinsaid plurality of ancilla qubits comprise a plurality offrequency-tunable ancilla qubits.
 14. The system for transmission ofquantum information for quantum error correction according to claim 1,wherein each of the ancilla qubits has a relaxation time and a coherencetime that is greater than 1 μs.
 15. The system for transmission ofquantum information for quantum error correction according to claim 1,wherein each of the data qubits has a relaxation time and a coherencetime that is greater than or equal to 75 μs.
 16. A method oftransmitting quantum information for quantum error correction,comprising: providing a plurality of ancilla qubits; providing aplurality of data qubits spaced apart from said plurality of ancillaqubits; mapping errors from said plurality of data qubits to saidplurality of ancilla qubits via virtual photons in a superconductingmicrowave transmission line; measuring said plurality of ancilla qubitsto detect said errors; and performing quantum error correction based onsaid detected errors.
 17. The method of transmitting quantum informationfor quantum error correction according to claim 16, wherein saidmeasuring said plurality of ancilla qubits gives a parity of saidplurality of data qubits.
 18. A quantum computer, comprising: arefrigeration system under vacuum comprising a containment vessel; anancilla qubit chip contained within a refrigerated vacuum environmentdefined by said containment vessel, said ancilla qubit chip comprising aplurality of ancilla qubits; a data qubit chip contained within saidrefrigerated vacuum environment defined by said containment vessel, saiddata qubit chip being spaced apart from said ancilla qubit chip andcomprising a plurality of data qubits; and an interposer containedwithin said refrigerated vacuum environment defined by said containmentvessel, said interposer being coupled to said ancilla qubit chip andsaid data qubit chip and comprising a dielectric material and aplurality of superconducting structures formed in said dielectricmaterial, wherein superconducting resonators comprising saidsuperconducting structures formed in said interposer enable transmissionof quantum information between said plurality of data qubits on saiddata qubit chip and said plurality of ancilla qubits on said ancillaqubit chip via virtual photons for quantum error correction.
 19. Thequantum computer according to claim 18, wherein each superconductingstructure of said plurality of superconducting structures extends from adata qubit of said plurality of data qubits to an ancilla qubit of saidplurality of ancilla qubits.
 20. The quantum computer according to claim19, wherein said data qubit has a first frequency, said ancilla qubithas a second frequency, and said superconducting resonator comprisingsaid superconducting structure formed in said interposer has a thirdfrequency, wherein said third frequency is sufficiently detuned fromsaid first frequency and said second frequency to prevent real photontransfer between said data qubit and said ancilla qubit.